What is everything? And even if Anna fucks around now, i.e. takes advantage of the opportunity, she is just as much a victim of this intrigue as David.
Anna in the gutter as a whore at the end? Would that be appropriate in return for the guilt of not having trusted her husband?
If Anna starts a new life with Jake at the end of the game, for example, and had every dick in town in her belly in between, David can have as much evidence in his hand as he wants, he remains the loser of this intrigue (and most here will celebrate that).
Even if David ends up getting sole custody of their daughter, it's not a happy ending for David. Everyone on the "street" will still laugh at him because they were allowed to fuck his wife.